Authorities were warned about the possibility of a jailbreak at the Orsainville Detention Centre near Quebec City months ago, sources tell Radio-Canada.
Three men remain on the lam after a daring helicopter escape at the facility Saturday evening.
The helicopter landed in the jail yard and transported the men away.
A police source confirmed to Radio-Canada that Sûreté du Québec investigators had details about a possible escape using a helicopter as far back as March.
The source told Radio-Canada that investigators took the concerns about a possible escape plot to prison authorities, but nobody took the plan seriously.
The escape was the second time in just over a year that a helicopter was used in a jailbreak in Quebec.
Two inmates made a similar escape from a St-Jérôme prison in March 2013, but they were caught by police within a few hours.
On Tuesday, Quebec Public Security Minister Lise Thériault said federal authorities have confirmed that no-fly zones will be imposed over Quebec detention centres.
They will be rolled out gradually.
Escapees awaiting trial
The three men involved in Saturday's escape were arrested in 2010 by provincial police after a drug operation bust in Abitibi known as Project Crayfish, which led to dozens of arrests.
Yves Denis, 35, Denis Lefebvre, 53, and Serge Pomerleau, 49, were awaiting trial on drug-related charges, as well as charges of murder and gangsterism.
Their whereabouts are still unknown.
According to Radio-Canada's source, the authorities knew that Maxime Lefebvre — the son of escapee Denis Lefebvre — had his helicopter licence.
The police knew that Denis Lefebvre was also a pilot and owned helicopters and that they might be used in an escape.
Christian Assad owns the helicopter school on Montreal's South Shore where the two learned to fly.
"They’re not the only pair of father and son that we’ve trained," Assad said.
"I think the father had some fixed-wing background, so he did like a conversion course, is what we call it, and the son did the full initial flying lessons.
"We gave them a licence like we do any other student."
Assad said he didn't remember anything remarkable about the pair.
A spokesperson for Quebec's public security minister said the department is looking into what changes can be made to prevent similar escapes from happening again.